Recovery of medicinal creosote



Patented Nov. 6, 1 951 2573941651: R OVERY M iii .LQFFICE imosorj 7'Lloyd '1. Sandborn, :Grossett;Arkguassignor to Crossett Lumber Company;afhoruoration .of

. Arkansas rawinsinp ti li ji Serial No. ;1 '743 PhiSinventioh relatesto improvement in the protests of separating creosote from the otherconstituents in' -theoils' which are obtainedby the destructivedistillation of wood.. #In addition to gii-ai-acoland creosol which arethe IIIOSll'dfir sir ahleconstituents of creosote these oils contain avariety of other phenolic constituents and also some acidie-and neutraLmaterials.

Heretofore publishedmethods-of isolating .creo, sote-from'suchbils haveusually involved. the follcwing'stepsz I T Treating the oils with asolution ofsodium hydroxide or equivalentalkali-to' dissolve phenolic'constituents. 'In some cases the 'oil is treated with sodium bicarbonateor sodium caribonat for the removal of acids before treatin lt'withsodium" hydroxide. 2'.'- Separating the layers. BQHeating the alkalinesolution of. phenolic material to steam distill off any neutral materialwhich may be'susp'ended in itt fA -r is usually blownthroughthe'solution during distillation. 'IAFA'cidifying the solution toliberate phenolic material which separates. as an oily layer I .5;Separating th'ecrude phenolic oil from the aqueous layer and washing itwith, water;

6. Fractional :distillation of the crude phenolic foil to. give aselected fraction with suitable boitingrange and specific gravity.

* Exactispecifi'cations for the product willvary v somewhat'depending onthe use to be made of the creosote. For some purposes at. the presenttime it is required that the specific gravity be not. less'than' 1.076at 25 C. and that 9.0% of the'imateria-l boil between 203 "and 220 6;:This material is sometimes calledBeechwood Creosote. 'Since-guaiacoland .creosol hare-higher specific grayities than'any of the otherconstitu- .ents,. specific gravity is a convenient -means of determininthe. q ality of, the finished product.- A hi h. pe fi av y i d a es a hih euaia nl eontent and: is, therefore c s dered, to Iceett r a apte tome icina purpo es- 7 Y -.;-'On n oe s' nv vin t e t ps'ist assribedleapensive and. time consumingbecause'it'is necessary to hefat fand coollarge volumes s ution and to distill an appreciable amount of y'gat'er,along with the organic matter that must 'yreinoved. In many vcases thesplutiom a er ling, still .contains'lsome insoluble mater ljin andseiaial.atitd'"only after prolonsedistanamg;

was li .3192271, R i ue use issued such fine" suspension that it can hesettled 611 112 55 "was .94

3 11;;aaioaaassistants with time sl t S In th t obiec nab" s id tin h hfro rv re l h and ereosol. "The specific gravity rves as a measureoftheir my, Q hat ari'additional advantage tie fdist lationresults fromthe met n method permits use 1 t isolutions'thereby-re e s e ling orsmaller volumes of setu- "rm'tt-ing substantial savings in cost uipmentrTests have shown that, by emi the solvent-method, products with satisfpecjficfgravity can be obtained-using '7, ,20fiandeven40% concentrationsof sodium hydroxide, while with the steamdistillation methed,'thequalityof the creosote asindicated byspecificgravity, drops "off withconcentrations above 5% -Witlr a sodium hydroxide concen- 'tr'ation'ofor more,there is a .tendencyzzfor solids to "separate from the alkalinesolution. The separation .of solids introduces mechanicaldifficulties..-in "handling the solution and while such difficulties arepurely mechanical it most convenient to avoid them by th 1550 1-5-.29%oonc entrationssof sodium hydrpxide I I I U d prese t e onom c. o dinslsodiumu 1 dioxide is the mo t f vorab a ka but quivalen a kalie su has pot s um 9r ih h droxide may be used With potassium hydroxide,concentra ion s h g -as 4 0% a e u ed withqutrthe separation of solids,

The fact that solvent extraction permits the use ofhigher'concentrations of sodium hydroxide than are feasible with, steamdistillation appears to result'from'the'faet that the crude wood oilcontains some low specific gravity constituents bility of thesematerials in the aqueous solutiontends to prevent their removal bydistillation with steam it does not prevent their being ex tracted fromthe aqueous olution with a solvent. Although many of the low specificgravity constituents which dissolve in the alkali are neutral, some ofthem appear to contain phenolic groups which exist in the free phenolcondition rather than in the phenolate condition. If the solvent whichis used for extraction of the alkaline solution is washed with anadditional amount of sodium hydroxide it is possible to recover anappreciable amount of material which has the 'same boiling range ascreosote but which has a much lower specific gravity. Obviously anymethod which permits the removal of these low specific gravityimpurities will improve the quality of the product.

I have found that the extraction step may be carried out with any liquidorganic solvent which is immiscible in water or with alkaline solutionsand which dissolves wood oils and which is chemically inert towardalkali and toward phenoliematerial under alkaline conditions. Solventswhich fail to meet these requirements are not suitable. Esters cannot beused because they react with alkali. Low molecular weight alcohols andketones are not suitable because they are soluble in water. Even normalbutyl alcohol, which is substantially immiscible with water at roomtemperature, has been found to be soluble in the alkaline solution ofcreosote and is also'unsuitable. Solvents such as benzyl chloride andallyl chloride in which the chlorines are unusually active areunsuitablebecause such compounds react with phenols in alkaline solutionto give ethers.

In most cases halogenated hydrocarbons are sufiiciently stable to permittheir use. However, to exclude the exceptions,

such solvents are defined as halogenated hydrocarbons in which thehalogens are stable under the conditions of extraction. Hydrocarbonsolvents such as petroleum ether can be used but they are less effectivesolvents for the constituents of wood oils.

By liquid solvents is meant solvents which are liquid under theconditions of extraction. While for reasons of economy I prefer to makesuch extractions at room temperature and under atmospheric pressure, Ido'not wish to limit myself to such conditions.

Solvents which are solid at room temperature but liquid at highertemperature can be used if extraction is done at elevated temperature.In case temperatures above 100 C. are used the extraction can be madeunder pressure sufficiently high to keep the water in liquid form.Likewise materials which are gases at ordinary temperature but which areliquid at lower temperatures or under superatmospheric pressure can beused if the extraction is made under increased pressure and at lowertemperature as long as the temperature is not so low that the aqueoussolution will solidify. It should be understood that the onlylimitations regarding temperature and pressure are those which assurethat both the aqueous solution and the solvent will be liquid underextraction conditions.

Aromatic hydrocarbons, ethers, and halogenated hydrocarbons in which thehalogen is stable under extraction conditions are suitable solvents forextraction. Such solvents are typical of a large group of solvents'whichcan be defined by the term a liquid organic solvent for wood oil, whichsolvent is immiscible with and is chemically inert toward alkalinesolutions of creosote.

Extraction should be continued, by either batch or continuous methods,until addition of water to a portion of the phenolate solution no longercauses turbidity. I have found that extraction of the alkaline solutionwith three 500 ml. portions of solvent for each liter of wood oiltreated represents a maximum beyond which it is not advisable to go. Inmost cases a single extraction with 500 ml. of solvent per liter of oilhas been adequate. Use of larger amounts of solvent lowers the yield ofcreosote slightly by the removal of v desirable phenolic. constituentsand therefore for economic reasons should be avoided; In one'case inwhich eight 500, ml. portions of solvent per liter of oil, insteadofthree, were used, the yield of creosote decreased from 16.2%;to 14.8%without any detectable improvement in quality of product. The solventmaybe recovered by distillation in known manner and reused in theprocess.

In respects other than those already stated the same precautions shouldbe employed in the sol;- vent extraction method as in conventionalprocedures. It is recommendedthat the usual-pro cautions be takenconcerning the selection of the amount of alkali. Attention is called tothe difference between concentration of alkali and amount of alkali.Although, the. amount ofrwood oil which will dissolvetin-the aqueousalkaline solution may be increased'by increasing'either theconcentration or the amount of alkali used, this increased solubilityresults from other causes. In the case of increased concentration thedis solved material is not held chemically and iseasily extractedfromithe aqueous solution with solvents. 'whenztheamount of alkali isincreased, larger amounts of phenolic materials are converted to.phenolates, which materials are not easilyext'rac'ted from the alkalinesolution.- It is well known that the phenols present in wood oil varyinithei'r ability to react with alkali and that those phenols which aremost readily dissolved in caustic alkali are those which are mostdesirable in the finished product, especially as regards ispecificgravity. Consequently it is conventional practice in the refining ofcreosote to use less than the amount of caustic required to remove allof the phenol. If too much alkali is used the specific gravity of theproduct will be lowered and'i'f too little alkali is used the yield ofproduct will be low.

Different batches of oil vary somewhat in alkali requirement; Since aconsiderable amount of such variations results from a variation in thedissolving the phenolic material in sodium hydroxide. 7 After suchremoval of organic acids, the

use of 150 grams of sodium hydroxide per liter of oil has been found toyield 16.71% of creosote with a specific gravity of1.0791 at 25 c. whichresult issatisfactory as regards both yield and quality of product. Theuse of 200 g. of sodium hydroxide gave a 24.85% yield of creosote withsp. g 1.07( l ,which is too low. and the use of.

proved pro cess con templates principally :the production l of fcreosote wnicn nieets the specifications for'mdlcinal-ci'eosote; thatis, creosote-with a specific gravity of notl'ess than-l;076 at 25 -0.and of which 90% or more boils between 203 and 220 C. at 760 mm. In caseit isdesired- "toobtain other grades of creosoteonto meeteither higherorlower specific gravity specifications, the information ,given above,as well as that contained in the examples hereinafter set forth, willpermit one skilled in theartto vary the quality ofthe product byvarylflg'the ainount-ofalkaliused.

After the extractiorrwith an organic solveii'tiis cpmpretemme alkalinesol d 7 n is adidifi 1 to aboutfi pI-I whereuponcriide creosote sepaates as an oily layer and the layersfare' separated. Any acid canbeusedfor this puirposegjdri neuof aqueous 1 solution. 1 The-aqueous's'elut extracted with three- 500' ml. portions of after which itwasacidified td'apprexlmately 6 pH-by theaddition of 593=ml.=ofi-2='50grams-per liter sulfuric acid solution. The 330 ml. ofp lieriri licoilwhich separated was washed- "with water and was thenfractionallydistilled; collecting the fraction boiling at 1124 37" o.attempt-. The yield 1 obtained was 1688 gr'ams -(16.2% o'f" crig-in-a'loil) of inaterial withsp. ge 1.0830 at'259-C. In this case-themewas-used a' -inch screen packed distillation-column ofthe' typedescribed in-In'di Eng-QChem. iA-nalgEd 1'5 290,-"1943. In other tests afour 'fdot vig'erauxc'olurnn or a 20 p'late' Bruuncolumnhavegiven-satisfactoryresults. I a T 5 The results [of otherexamples empmying-tne same procedure but with variations in concehtrations of sodium hydroxide and type of solvent ion w used aresummarized below-,- one'lite'r of w ood oil' being tre'ated'ine'ach-eiample: A

- Solvent MIJNaOH gggfi e gf SP G Per cent' 1, 500 10 16. 21 l. 0830 75020 17. 32 1. 0827 do 375 19.62 1. 0770 Carbon Tetrachloride. 1,500 1016.90 1.0775 5 Ethyl Ether 1, 500 10 17. 18 1. 0789 6 Petroleum Ether1,500 10 20.77 1.0723

tralization can be accomplished by passing carbon dioxide gas into thealkaline solution. If desired, gases containing carbon dioxide, such asstack gases or the gases from lime kilns, can be used. In most cases itwill be more convenient to use sulfuric acid. The resulting crudecreosote can be distilled directly although it is best to wash it withwater before distillation to remove traces of inorganic salts whichmight otherwise cause foaming of the liquid or incrusting of heatexchange surfaces.

The crude oil is usually distilled under reduced pressure taking suchfraction as meets the required specifications for any specific grade ofcreosote. It has been found that at mm. pressure the fraction boilingbetween 112 and 137 C. has the boiling range of medicinal creosote. Theconditions of distillation may be varied as regards pressure and type ofstill and column so long as the usual precautions known to those skilledin the art are taken. 7

This process can be applied to any oil containing guaiacol and creosolbut the advantages of the process are most evident in the processing ofoils which are obtained by the distillation of wood. The exact method ofObtaining such oils will vary depending on the method of treating thewood distillation product. One useful oil is a fraction boiling at195-230 C. which oil is distilled from the tar that settles frompyroligneous acid. The residual oil from methyl alcohol stills and whichis called alcohol oil, may also be treated in accordance with myimproved process to obtain creosote.

The process just described is illustrated further by way of thefollowing example, using a wood oil having a boiling range from 195--230C. which has been distilled from the tar that settles from pyroligneousacid.

A one liter sample of wood oil, weighing 1042 g., was washed with anequal volume of a 10% sodium carbonate solution. The oil layer was thenwashed with 1500 ml. of a 10% sodium hydroxide solution giving a 300 ml.layer of oil and 2080 ml.

The material obtained in Example 6, it will be noted, has a specificgravity below that required for medicinal creosote. It was found that bytak ing only the material boiling at 112-131.5 C./50 mm. there wasobtained a 14.35% yield of material with sp. g. 1.0775.

The step in the separation of creosote from wood oil with which thisinvention is most concerned is that of removing objectionable materialby means of a solvent extraction instead of the usual method of steamdistillation. It is to be understood that at other stages in the processit is possible to use any of the known means of accomplishing thepurposes which have been hereinbefore mentioned.

From the foregoing it will be apparent that I have devised an improvedprocess for recovering creosote from oils containing the same which issimple and economical and by means of which large yields may beobtained. While I have described several ways of carrying out myinvention it will be understood that it is not to be limited thereto butthat it is susceptible of various changes and modifications withoutdeparting from the spirit thereof, and I desire, therefore, that onlysuch limitations shall be placed thereupon as are specifically set forthin the appended claims.

What I claim is:

1. In the process of recovering medicinal creosote from an aqueousalkaline phenolate solution formed by reacting wood oils with an aqueoussolution of caustic alkali, the step which consists in extracting fromsaid solution only those constituents having a lower specific gravitythan the product sought with a liquid organic solvent for wood oil whichis immiscible in and chemically inert toward said aqueous alkalinesolution.

2. The step defined in claim 1 in which the solvent employed is benzene.

3. In the process for removing medicinal creosote from an aqueousalkaline phenolate solution formed by reacting wood oils with an aqueoussolution of caustic alkali, the step which consists in extracting fromsaid solution only those con- 5. In the process for recovering-medicinalcreosote from woodoils, the steps which consist inv reacting saidoilswith an aqueous solution of caustic alkali having a concentration offrom 7 to 40% to form an aqueous alkaline phenolate solution, andextracting from said aqueousalkaline phenolate solution only thoseconstituents having a lower specific gravity than the product soughtwith a liquid organic solvent for wood oils which is immiscible in andchemically inert toward said aqueous alkaline solution,

y 6. In the process for removing medicinal creosote from wood oils,thesteps which consist in reacting said oils with an aqueous solution ofcaustic alkali having a concentration of from 7 to 40% to form anaqueous alkaline phenolate solution and extracting fromsaidaqueousamaline phenolate solution only; those :ponstituents' havinga lower specific gravity than theproduct sought with benzene in aplurality of extractions in which approximately 500 m1. of benzene isemployed per liter of wood oil being treated.

LLOYD T. SANDBORN.

REFERENCES CITED The following references are of recordlin the file ofthis patent: v

UNITED STATES PATENTS Number Name h 7 Date v 1,651,617 Moser Dec. 6,1927 2,043,102 I Kester June 2,1936 2,298,816 Ambler Oct. 13,19422,301,270 Gerlicher Nov. 10, 1942 2,313,385 Levesque Mar. 9, 19432,342,386 Berger et' a1 Feb. 22, 1944 2,357,252 Berger et al Aug. 29,1944 2,358,979 Isham et a1 Sept. 26, 1944 2,523,154 Shmidl Sept. 19,1950

1. IN THE PROCESS OF RECOVERING MEDICINAL CREOSOTE FROM AN AQUEOUSALKALINE PHENOLATE SOLUTION FORMED BY REACTING WOOD OILS WITH AN AQUEOUSSOLUTION OF CAUSTIC ALKALI, THE STEP WHICH CONSISTS IN EXTRACTING FROMSAID SOLUTION ONLY THOSE CONSTITUENTS HAVING A LOWER SPECIFIC GRAVITYTHAN THE PRODUCT SOUGHT WITH A LIQUID ORGANIC SOLVENT FOR WOOD OIL WHICHIS IMMISCIBLE IN AND CHEMICALLY INERT TOWARD SAID AQUEOUS ALKALINESOLUTION.